Abstract: The thermal decomposition kinetics of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)(PHBV) has been investigated by means of non-isothermal TG-DTA with various heating rates of 5.0, 10.0, 15.0, and 20.0 K•min^-1. The result shows that the decomposition process of PHBV is composed of three stages：initial stage, medium stage, and end stage. The most probable kinetic function of the initial stage is the Avrami-Erofeev equation with n=1/2, and the corresponding machanism is controlled by random nuclear producing and growing process. The apparent activation energy (Ea(β→0)) and the pre-exponential constant(A(β→0)) are 69.44 kJ•mol^-1 and 10^6.27 s^-1 respectively. The most probable kinetic function of the medium stage is the Avrami-Erofeev equation with n=2/5, and the corresponding machanism is the same with the previous stage. The apparent activation energy (Ea(β→0)) and the pre-exponential constant (A(β→0)) are 117.64 kJ•mol^-1 and 10^11.48 s^-1 respectively. The most probable kinetic function of the end stage is the exponential function with n=1/3, and the corresponding mechanism follows Mampel Power theorem. The apparent activation energy(E_a(β→0)) and the pre-exponential constant (A(β→0)) are 116.64 kJ•mol^-1 and 10^8.68 s^-1 respectively.